The TTL8 board is a new board that we have recently put out on Tindie (https://www.tindie.com/products/tymkrs/tymkrs-ttl8-module/) and not only is it small and compact, it’s quite useful for turning on and off low current loads such as LEDs.
The board consists of a shift register, 8 leds (or not), and headers for input into the shift register, output from the shift register, and header space for daisy chaining for multiple TTL8 boards. If you’ve ever worked with the 74hc595 shift register (or any shift register in general), the number of wires required to get one of those bad boys working is a pretty prohibitive pain in the butt. For example, see the following:
I’m anti clusters of wires. So the board takes all of those wires and puts them into a 5/8” x 1-1/8” footprint. As a stand-alone board, for just LED indication, you only need your microcontroller and 5 wires going to the Port In side: (from left to right) Power, GND, Latch, Clock, Serial.
Most of the microcontrollers I work with use 3.3v. And you can certainly connect the TTL8 board to the microcontroller, or you can, if you’re daisy chaining a bunch of TTL8 boards, use the power and gnd header on the bottom left with greater current capabilities. Just note that voltage-wise, your uC voltage needs to be the same as that provided to the board. So if your microcontroller works off of 3.3v, provide your TTL8 board with 3.3v.
If you want the shift register to drive 8 other items, or even 8 LEDs that aren’t attached to the board, that’s how you’d use 0-7 header. The shift register is connected to all 8 of the pins and can drive whatever you’d like - within current limits of the shift register of course.
Whisker uses this board as a debug board - so if you want to check if your input device is actually working as expected, or sending signals as desired, you can have it light up the LEDs.
So this is of course using the Propeller microcontroller. I used the demo board and programmed it in Spin. In the main body of the program, the propeller sets the pins sending out Latch, Clock, and Serial as outputs. It then repeatedly monitors to see whether a key’s been pressed. If it has, it puts it into register dirb.
And repeating from index 0 to 7, it spits out via serial what key has been pressed in register dirb. If you had 4 TTL8 boards chained together, you’d repeat index 0 to 31.
So it spits out the serial, then it outputs a 1 on the clock line to bring it high, then brings it low to signify that a bit has been set, and that the next bit can be set in the shift register. Then after all index values have been gone through, the latch is set high and low again. This feeds it out to the indicator leds, or to whatever you’re driving.
And that’s the TTL8 board! Again it’s available: https://www.tindie.com/products/tymkrs/tymkrs-ttl8-module/ and if you have any questions, let us know!